Electrophotographic element containing phthalocyanine

ABSTRACT

An electrophotographic plate comprising phthalocyanine pigment dispersed in a binder material is disclosed. Methods of preparing and using said plate in electrophotographic processes are also disclosed.

1 June 11, 1974 1 ELECTROPHOTOGRAPHIC ELEMENT CONTAININGPHTI-IALOCYANINE [75] Inventor: John F. Byrne, Worthington, Ohio [73]Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: Jan. 3, 1966 [21] Appl. No.: 518,450

Related US. Application Data [63] Continuation-impart of Ser. No.375,191, June 15,

1964, abandoned.

[52] US. Cl 96/1.5, 96/1 R, 96/1.2, 96/1.6, 101/462, 101/457 [51] Int.Cl G03g 5/06 [58] Field of Search 96/1.5-1.8; 260/3l4.5, 88.3, 80.72,41; 252/501 [5 6] References Cited UNITED STATES PATENTS 2,168,5768/1939 Niemann 18/50 2,302,305 11/1942 Farrell 260/39 2,489,226 11/1949Morris 260/41 2,546,724 3/1951 106/288 2,602,756 6/1952 106/1932,649,382 8/1953 106/193 2,663,636 12/1953 Middleton 96/l.5 2,901,3498/1959 Schafi'ert et al. 96/1 2,955,938 10/1960 Steinhilper 96/13,038,799 6/1962 Metcalfe et a1 96/1 3,092,493 6/1963 Kaiser 96/13,155,503 11/1964 Cassiers et a1. 96/1 3,159,483 12/1964 Behmenberg eta1 96/1 3,308,444 3/1967 Ting 390/173 FOREIGN PATENTS OR APPLICATIONS1,258,844 3/1961 France OTHER PUBLICATIONS Grieg, An OrganicPhotoconductive System, RCA Review, Vol. 23, Sept. 1962, pages 413-419.Winslow et a1., JACA 77, 1955, page 4,754.

Tollin, J. Chem. Phys. 32, N0. 4, 1960, pages l,020l,025.

Maier et al., Zeit. fur Phys. Chem. 39, 1963, page 250. Condensed Chem.Dictionary, 6th Ed. 1961), Reinhold, pages 892-893.

Moser et a1., Phthalocyanines Compds, ACS No. 157, 1963, pages 69-76.

Primary ExaminerRo1and E. Martin, Jr.

[57] ABSTRACT An electrophotographic plate comprising phthalocyaninepigment dispersed in a binder material is disclosed. Methods ofpreparing and using said plate in electrophotographic processes are alsodisclosed.

27 Claims, 2 Drawing Figures PATMEMM m4 INTENSITY MB; 1 1 a SHEET 1 [1F2 ATTORNEYS PATENT-mum m I mm 1 m SHEET 2 0f 2 INTENSITY X FORM l I l ll l l l l l l I 1 I600 I400 I200 I000 80250 600 l FREQUENCY (CM INVENTORFIG. 2 BY MHWBNE ATTORNEYS This application is a continuation-in-part ofparent application Ser. No. 375,191, filed in the United States PatentOffice on June 15, 1964, now abandoned.

This invention relates to electrophotography and more particularly to abinder plate usable in xerography.

In the art of xerography as originally disclosed by Carlson in US. Pat.No. 2,297,691, an electrostatic latent image is formed on aphotoconductive insulating layer and is developed'thereon by finelydivided electroscopic developing materials. The developed image may thenbe fixed in place or transferred to a copy sheet where it is permanentlyfixed. Generally the photoconductive insulating layer is first chargedto sensitize it and is then exposed to a light image or other pattern ofactivated electromagnetic radiation to dissipate the charge in radiationstruck areas. Thus the charge pattern formed conforms to theelectromagnetic radiation pattern which impinges upon the plate. Thischarge pattern may then as above discussed be developed or made visibleby a charge wise deposition on the plate of an electroscopic orelectrostatically attractable, finely divided colored material which isreferred to in the art as toner.

As disclosed in the above noted Carlson patent, suitable inorganic andorganic materials may be used to form the photoconductive insulatinglayer on which the latent electrostatic image is formed. Otherphotoconductive materials have been disclosed in the piror art as beinguseful in similar electrophotographic proc esses such as in US. Pat.Nos. 2,357,809; 2,891,001; and 3,079,342. Some of these materials arevitreous selenium, polymers such as 'polyvinylcarbazole, and resinsuspensions of inorganic photoconductive pigments such as, for example,zinc oxide and cadmium sulfide. While most of these materials haveevidenced some commercial utility, there are certain inherentdisadvantages to the commercial use of each of the suggestedcompositions.

The discovery of the photoconductive insulating properties of highlypurified vitreous selenium has resulted in this material becoming thestandard in commercial xerography. Vitreous selenium, however, issensitive only to wave lengths shorter than about 5,800 A. U. Inaddition, xerographic plates made with selenium are expensive tomanufacture since this material must be applied to the supportingsubstrate by vacuum evaporation under carefully controlled conditions.Also, vitreous selenium layers are only meta-stable and may bere-crystallized into inoperative crystalline forms at temperatures onlyslightly in excess of those prevailing in conventional xerographiccopying machines.

Other known xerographic plates made with certain aromatic organicphotoconductors have relatively low sensitivity to light and have mostof this sensitivity in the ultra-violet range, which is not fullysatisfactory for use in conventional electrophotographic copyingdevices. Even the most sensitive organic photoconductive polymers leavemuch to be desired for commercial purposes. The choice of materialsavailable for use in aromatic polymeric plates is of course limitedbecause of the necessity of the selection of an already photoconductivematerial. In addition, all of the above noted xerographic plates lackabrasion resistance and stability of operation particularly at elevatedtemperatures.

Binder plates containing zinc oxide pigments, while comparativelyinexpensive, are lower in sensitivity as compared with vitreous seleniumplates and are not reusable. Also, as above noted, their visiblesensitivity is quite limited. Furthermore, it is necessary to use suchhigh percentages of photoconductive pigment in order to attain adequatesensitivity that it is difficult in zinc oxide plates to obtain smoothsurfaces which lend themselves to efficient toner transfer andsubsequent cleaning prior to reuse. An additional drawback in the use ofzinc oxide binder type plates is that they can be sensitized only bynegative and not by positive corona. This property makes themcommercially undesirable since negative corona discharge generates muchmore ozone than positive corona discharge and is generally harder tocontrol.

It is therefore an object of this invention to provide a novelelectrophotographic plate devoid of the above noted disadvantages.

Another object of this invention is to provide electrophotographicallyreusable plates having sensitivities which extend over substantially theentire visible spectrum.

- Still another object of this invention is to provide a Yet a stillfurther object of this invention is to provide a novel xerographicprocess wherein a reusable plate is utilized which has exceptionalmechanical strength and hardness, high temperature and abrasionresistance under substantially normal conditions of xerographic machineoperation.

Yet a further object of this invention is to provide highly sensitivepanchromatic compositions which may be used in xerographic,xeroprinting, hydroprinting, heat deformable and lithographic processes.

Still a further object of this invention is to provide materials whichmay be used in the manufacture of flexible printing plates adapted foruse in flexographic printing processes.

Still a further object of this invention is to provide a materialsuitable for use in the manufacture of reusable plates useful in colorxerography and other electrophotographic processes.

Yet a still further object of this invention is to provide panchromaticxerographic plates of substantially high resolution for use inmicro-printing and imaging applications.

The foregoing objects and others which will become apparent from thefollowing description are accomplished in accordance with thisinvention, generally speaking, by providing a novel photoconductivelayer containing a phthalocyanine in a film forming binder in a plateadapted for use in electrophotography. This photoconductive layer hasparticular utility in a xerographic process where reusability of theplate is desired. The phthalocyanine-binder photoconductive layer may becast as a self-supporting film, or in lieu thereof may be deposited onany suitable supporting substrate. The plate formed may be both with orwithout an overcoating on the photoconductive layer. AS a thirdalternative to the above noted self-supporting layer and substratesupported layer, the phthalocyanine-resin photoconductive layer may beused in the formation of multi-layer sandwich configuration Xerographicplates.

It has been found in the present invention that suspensions ofphthalocyanine pigments in insulating binders are not only capable ofsustaining the very high fields required in commercial xerography, butare also highly photoconductive whether or not the binder itself isphotoconductive. Since a wide variety of binders may be used in thepresent invention, including not only photoconductive materials but alsovarying for example, from soft thermoplastics to hard cross linkedenamels, and since percentages of phthalocyanine required in thesecompositions are relatively low, the mechanical properties of thephotoconductive layers are substantially determined by the properties ofthe binders. This is highly desirable since the selection of thephotoconductive layer to be used may therefore be varied over a widerange by selection of the appropriate binder to suit the specificrequirements of each particular situation. In this regard, thesephotoconductive layers are substantially different from the heretoforeknown binder suspensions of inorganic pigments which require such a highpercentage of inorganic pigment that the inorganic pigment usedessentially controls the physical properties of the finalphotoconductive layer.

The binder may itself be a photoconductive material or contain aphotoconductive material blended into it. Other organic or inorganicphotoconductive pigments may also be dispersed in the binder along withthe phthalocyanine regardless of the photoconductivity of the binder.

When it is desired to coat the phthalocyanine-binder film on asubstrate, various supporting materials may be used. Suitable materialsfor this purpose are aluminum, steel, brass, metallized or tin oxidecoated glass, semi-conductive plastics, and resins, paper and any otherconvenient material. Any suitable dielectric material may be used toovercoat the photoconductive layer. A typical overcoating is bichromatedshellac.

Any suitable phthalocyanine may be used to prepare the photoconductivelayer of the present invention. The phthalocyanine used may be in anysuitable crystal form. It may be substituted or unsubstituted both inthe ring and straight chain portions. Reference is made to a bookentitled Phthalocyanine Compounds by F. H. Moser and A. L. Thomas,published by the Reinhold Publishing Company, 1963 edition for adetailed description of pththalocyanines and their synthesis. Anysuitable phthalocyanine may be used in the present invention.Phthaloycanines encompassed within this invention may be described ascompositions having four isoindole groups linked by four nitrogen atomsin such a manner so as to form a conjugated chain, said compositionshave the general formula (C H N R wherein R is selected from the groupconsisting of hydrogen, deuterium, lithium, sodium, potassium, copper,silver, beryllium, magnesium, calcium, zinc, cadmium, barium, mercury,aluminum, gallium, indium, lanthanum, neodymium, samarium, europium,gadolinium, dysprosium, holmium, erbium, thulium, ytterbium, lutecium,titanium, tin, hafnium, lead, silicon, gervanium, thorium, vanadium,antimony, chromium, molybdenum, uranium, manganese, iron, cobalt,nickel, rhodium, palladium, osmium, and platinum; and n is a value ofgreater than 0 and equal to or less than 2. Any other suitablephthalocyanines such as ring or aliphatically substituted metallicand/or non-metallic phthalocyanines may also be used if suitable. Asabove noted, any suitable phthalocyanine may be used to prepare thephotoconductive layer of the present invention. Typical phthalocyaninesare: aluminum phthalocyanine, aluminum polychlorophthalocyanine,antimony phthalocyanine, barium phthalocyanine, berylliumphthalocyanine, cadmium hexadecachlorophthalocyanine, cadmiumphthalocyanine, calcium phthalocyanine, cerium phthalocyanine, chromiumphthalocyanine, cobalt phthalocyanine, cobalt chlorophthalocyanine,copper 4-aminophthalocyanine, copper bromochlorophthalocyanine, copper4- chlorophthalocyanine, copper 4nitrophthalocyanine, copperphthalocyanine, copper phthalocyanine sulfonate, copperpolychlorophthalocyanine, deuteriophthalocyanine, dysprosiumphthalocyanine, erbium phthalocyanine, europium phthalocyanine,gadolinium phthalocyanine, gallium phthalocyanine, germaniumphthalocyanine, hafnium, phthalocyanine, halogen substitutedphthalocyanine, holmium phthalocyanine, indium phthalocyanine, ironphthalocyanine, iron polyhalophthalocyanine, lanthanum phthalocyanine,lead phthalocyanine, lead polychlorophthalocyanine, cobalthexaphenylphthalocyanine, copper pentaphenylphthalocyanine, lithiumphthalocyanine, lutecium phthalocyanine, magnesium phthalocyanine,manganese phthalocyanine, mercury phthalocyanine, molybdenumphthalocyanine, naphthalocyanine, neodymium phthalocyanine, nickelphthalocyanine, nickel polyhalophthalocyanine, osmium phthalocyanine,palladium phthalocyanine, palladium chlorophthalocyanine,alkoxyphthalocyanine, alkylaminophthalocyanine,alkylmercaptophthalocyanine, aralkylaminophthalocyanine,aryloxyphthalocyanine, arylmercaptophthalocyanine, copper phthalocyaninepiperidine, cycloalkylaminophthalocyanine, dialkylaminophthalocyanine,diaralkylaminophthalocyanine, dicycloalkylaminophthalocyanine,hexadecahydrophthalocyanine, imidomethylphthalocyanine, 1,2naphthalocyanine, 2,3 naphthalocyanine, octaaxaphthalocyanine, sulfurphthalocyanine, tetraazaphthalocyanine,tetra-4-acetylaminophthalocyanine, tetra-4-aminobenzoylphthalocyanine,tetra-4- aminophthalocyanine, tetrachloromethylphthalocyanine,tetradiazophthalocyanine, tetra-4,4-dimethyloctaazaphthalocyanine,tetra-4,S-diphenylenedioxide phthalocyanine, tetra-4 ,5-diphenyloctaazaphthalocyanine, tetra-( 6-methylbenzothiazoyl)phthalocyanine, tetra-pmethylphenylaminophthalocyanine,tetramethylphthalocyanine, tetra-naphthotriazolylphthalocyanine,tetra-4-naphthylphthalocyanine, tetra-4- nitrophthalocyanine,tetra-peri-naphthylene-4,5-octaazaphthalocyanine,tetra-2,3-phenyleneoxide phthalocyanine,tetra-4-phenyloctaazaphthalocyanine, tetraphenylphthalocyanine,tetraphenylphthalocyanine tetracarboxylic acid,tetraphenylphthalocyanine tetrabarium carboxylate,tetraphenylphthalocyanine tetra-calcium carboxylate,tetrapyridyphthalocyanine,tetra-4-trifluoromethylmercaptophthalocyanine, tetra-4-trifluoromethylphthalocyanine, 4,5-thionaphtheneoctaazaphthalocyanine,platinum phthalocyanine, potassium phthalocyanine, rhodium phthalocyane,samarium phthalocyanine, silver phthalocyanine, silicone phthalocyanine,sodium phthalocyanine, sulfonated phthalocyanine, thoriumphthalocyanine, thulium phthalocyanine, tin chlorophthalocyanine, tinphthalocyanine, titanium phthalocyanine, urnaium phthalocyanine,vanadium phthalocyanine, ytterbium phthalocyanine, zincchlorophthalocyanine, zinc phthalocyanine, others described in the Mosertext and mixtures, dimers, trimers, oligomers, polymers, copolymers ormixtures thereof.

Any-suitable insulating, film forming binder whether organic orinorganic may be used in combination with the phthalocyanine to preparethe photoconductive layer of this invention. In order to be useful, thebinder used in the present invention must be more resistive than aboutl0 and preferably more than ohm/cm. under the conditions of xerographicuse. It is to be understood that the term insulating as used hereincludes both photoconductive insulating material and conventionalinsulators which are substantially nonresponsive to light exposure.Typical photoconductive insulating materials include films of amorphousselenium, sulfur, sulfur-selenium mixtures, arsenicselenium mixtures,selenium-tellurium mixtures, lead oxide, cadmium sulfide, zinc sulfideand organic photoconductors (especially when these are complexed withsmall amounts of suitable Lewis acids). Typical of these organicphotoconductors are polyvinylcarbazole; polyvinylanthracene;4,5-diphenylimidazolidinone; 4,- S-diphenylimidazolidinethione;4,5-bis-(4- aminophenyl)-imidazolidinone; l,5-cyanonaphthalene;1,4-dicyanonaphthalene; aminophthalodinitrile; nitrophthalidinitrile;l,2,5,-tetraazacyclooctatetraene- (2,4,6,8);3,4-di(4-methoxy-phenyl)-7,8-diphenyll,2,5,6-tetraazacyclooctatetraene-(2,4,6,8); 3,4-di (4-phenoxy-phenyl-7,8-diphenyll ,2,5,6-tetraazacyclooctatetraene-( 2,4,6,8 3,4,7,8-tetramethoxyl,2,5,6-tetraaza-cyclooctatetraene-( 2,4,6,8); 2-mercaptobenzthiazole; Z-phenyl-4'diphenylideneoxazolone;2-phenyl-4-p-methoxy-benzylideneoxazolone;6-hydroxy-2-phenyl-3-(p-dimethylamino phenyl)-benzofuran;6-hydroxy-2,3-di(p-methoxyphenyl)-benzofuran;4-dimethylaminobenzylidenebenzhydrazide;4-dimethylaminobenzylideneisonicotinic acid hydrazide;furfurylidene-(2)-4- dimethylamino-benzhydrazide;S-benzilideneaminoacenaphthene; 3-benzylideneamino-carbazole; (4-N,N-dimethylamino-benzylidene)-p-N,N- dimethylaminoaniline;(2-nitro-benzylidene)-p-bromoaniline; N,N-dimethyl-N-(2-nitro-4-cyanobenzylidene)-p-phenylene-diamine;2,4-diphenylquinazoline; 2-( 4'-amino-phenyl)-4-phenylquinazoline;2-phenyl-4-(4'-dimethyl-amino-phenyl)- 7-methoxy-quinazoline;l,3-diphenyltetrahydroimidazole; l,3-di(4"-chlorophenyl)-tetrahydroimidazole; l ,3-diphenyl-2-4'-dimethyl aminophenyl)-tetrahydroimidazole; l,3-di-(p-tolyl)-2- quinolyl-(2--tetrahydroimidazole; 3-(4- dimethylamino-phenyl )-5 4'-methoxyphenyl-6-phenyll ,2,4-triazine; 3-pyridil-(4 )-5-( 4'dimethylamino-phenyl)-6-phenyl-1,2,4-triazine; 3,(4'- amino-phenyl )-5,6-di-phenyl-1,2,4-triazine; 2,5-bis 4'- amino-phenyl-(l')-l,3,4-triazole; 2,5-bis 4(N-ethyl- N-acetyl-amino)-amino)-phenyl-( l -1,3,4-triazole; 1,S-diphenyl-3-methyl-pyrazoline; l,3,4,5-tetraphenylpyrazoline; l-methyl-2-( 3 '4-dihydroxymethylenephenyl)-benzimidazole; 2-(4'-dimethylamino phenyl(-benzoxazole; 2-(4-methoxyphenyl)-benzthiazole; 2,5- bisp-aminophenyl-(l) -l,3,4-oxadiazole; 4,5- diphenylimidazolone; 3-aminocarbazole;copolymers and mixtures thereof. Typical insulating film forming bindersinclude thermoplastic and thermoset polymers such as polyvinylchloride,polyvinylacetates, polystyrene, polystyrene-polybutadiene copolymer,polymethacrylates, polyacrylics, polyacrylonitriles, silicone resins,chlorinated rubber, epoxy resins including halogenated epoxy and phenoxyresins, phenolics, epoxyphenolic copolymers, epoxy urea formaldehydecopolymers, epoxy melamine formaldehyde, polycarbonates, polyurethanes,polyamides, saturated polyesters, unsaturated polyesters cross-linkedwith vinyl monomers and epoxy esters, vinyl epoxy resins, tall-oilmodifled epoxys, and copolymers and mixtures thereof. Other insulatingfilm-forming binder materials include organics such as sucrose and itsderivates, rosin and modified rosins etc; inorganic materials such aslow melting point insulating glasses including those made fromglass-forming oxides, sulfides, selenides, borates, phosphates,arsenates, other well known glass formers and mixtures thereof. Inaddition to the above noted materials, any other suitable binder may beused if desired.

The phthalocyanine pigments may be incorporated in the dissolved ormelted binder by any suitable means such as strong shear agitation,preferably with simultaneous grinding. These methods include ballmilling, roller milling, sand milling, ultrasonic agitation, high speedblending and any desirable combination of these methods. In addition toadding the phthalocyanine pigment to the dissolved or melted bindermaterial it may also be added and blended into a dry or slurried form ofthe powdered binder material before it is heated or dissolved to make itfilm forming. Any suitable range of pigment-resin ratio may be used; ona phthalocyanine pigment-dried binder weight basis, this range extendsfrom about l/l to about l/lOO while the preferred range extends fromabout A to about 1 l 5. Optimum results are obtained when ratios fromabout 1/6 to about l/l2 are used and accordingly this range is mostpreferred. It should be noted in this regard that the preferred range ofcomponents lies substantially below that used in making heretofore knowninorganic photoconductor-binder plates which are generally quiteunsatisfactory in sensitivity when the pigmentbinder ratio drops belowabout 2/1. Other photoconductive pigments may also be added to theysystem when phthalocyanine is used in the ratios given above.

The ability in the present invention to use lower pigment to binderratios represents a highly desirable advantage over the prior art sincea smaller proportion of the relatively expensive organic pigmentcomponent is required permitting very smooth adhesive coatings to beobtained because of the high binder content. A much wider latitude ofmaterial is also accomplished by the present invention since thephysical properties of the plates may be determined substantially byselection of the binder; because the physical properties are littleaffected by the presence of the pigment. Thus, one may choose bindershaving the desired softening range, smoothness, hardness, toughness,solvent resistance, or solubility, water repellencyphotoconductivity andthe like with assurance that the pigment will not affect theseproperties to any considerable extent.

The pigment-binder-solvent slurry (or the pigmentbinder-melt) may beapplied to conductive substrates by any of the well-known painting orcoating methods, including spray, flow coating, knife-coating,electrocoating, Mayer bar drawdown, dip coating, reverse roll coating,etc. Spraying in an electric field may be preferred for smoothest finishand dip coating for convenience in the laboratory. The setting, drying,and/or curing steps for these plates are generally similar to thoserecommended for films of the particular binders used for other paintingapplications. For example, phthalocyanine-epoxy plates may be cured byadding a cross-linking agent and stoving according to approximately thesame schedule as other baking enamels made with the same resins, andsimilar pigments for paint applications. A very desirable aspect of thephthalocyanine pigments is that they are stable against chemicaldecomposition at the temperatures normally used for a wide variety ofbake-on enamels, and therefore may be incorporated in very hard glossyphotoconductive coatings, similar to automotive or kitchen applianceresin and glass enamels.

The thickness of the phthalocyanine films may be varied from about I tohundreds of microns, depending on the required individual needs.Self-supporting films, for example, cannot usually be manufactured inthicknesses thinner than about 10 microns, and are easiest to handle anduse in the to 75 micron range. Coatings, on the other hand, arepreferably in the 5 to 80 micron range for most uses. For certaincompositions and purposes it is desirable to provide an overcoating;this should usually not exceed the thickness of the photoconductivecoating, and preferably not above A of the latter. Any suitableovercoating material may be used such as bichromated shellac. A seriesof detailed examples indicating our preferred procedure of making theplate by mixing, milling, coating and the like is presented below.

While any suitable phthalocyanine or mixtures of phthalocyanines may beused in the present invention, it has been found that for best resultsin xerographic processes, a non-substituted metal-free phthalocyanine ismuch preferred over the others. As above noted, phthalocyanines usefulin the present invention include all the crystal forms of metal-freephthalocyanines such as alpha, beta, and what is hereinafter referred toas the X form of phthalocyanine. The exact physical structure of the Xcrystalline form phthalocyanine is not presently understood, however itis recognized as being different from the alpha, beta and gamma forms byits distinct x-ray diffraction pattern and its infrared spectrum.

The diffraction pattern and the spectrum are indicated in attached FIGS.1 and 2, respectively.

Referring now to FIG. 1, there is seen four x-ray diffraction curves invertical alignment for easy comparison. The uppermost curve is for alphaform, the second is for beta form, the third is for gamma form and thefourth is an experimental curve for X-form. The curves for alpha, betaand gamma forms are taken from C. Hamann and M. Starke, Investigation ofthe Electrical and Thermo-electric Properties of the Modification ofMetal-free Phthalocyanine," Phys. stat. Vol. 4, 509 (1964). As can beseen from FIG. 1, it is not possible to make a clear cut distinctionbetween alpha and gamma forms. Gamma form may merely be a highlyamorphous modification of alpha phthalocyanine. However, the curve forX-form may be easily distinguished. As seen in FIG. 1, the spectra forX-form has peaks at Bragg angles of about 17.3 and 22.3 which exist innone of the a, B and y polymorph spectra. Also, the peak at about 9.1 inthe X-form spectra is not present in the spectra of a and 7 forms. Majorpeaks for X- forrn fall at Bragg angles of about 7.5, 9.1, 16.7, 17.3and 22.3. All X-ray measurements were made with Copper K radiationhaving a wavelength of 1.54050 Angstrom Units.

FIG. 2 shows a comparison between an experimentally obtained infraredspectra for X-form metal-free phthalocyanine and infrared spectra foralpha, beta and gamma metal-free phthalocyanine obtained from theliterature. These curves are arranged in vertical alignment for easycomparison. These curves are conventional infrared spectra, plottingintensity against frequency in cm. The spectra for alpha, beta and gammaphthalocyanine are taken from the Hamann and Starke article cited above.Again, it can be seen that there is very little, if any, differencebetween alpha and gamma phthalocyanine. This strengthens the hypothesisthat gamma phthalocyanine is merely a more amorphous form of alphaphthalocyanine. The infrared spectra for X-form can be easilydistinguished from the reported spectra for alpha, beta and gamma forms.The variation in peak intensity and location for the differentpolymorphic forms is expecially noticeable in the 700800 cm and l250l350cm regions.

Specific preparations of the alpha, beta and X forms of phthalocyanineare as follows.

Preparation of Alpha Metal-Free Phthalocyanine Lithium phthalocyanine,86.7 g. is added to 600 ml. of well stirred concentrated sulfuric acidat 0C. The mixture is then stirred at this temperature for 2 hours. Theresultant solution is then filtered through a coarse sintered glassfunnel and poured slowly and with stirring into 4 liters of ice andwater. After sitting for several hours, the mixture is filtered and thecake is washed to neutrality with water. The cake is then finally rinsedwith methanol several times and dried in air. The resultant powder isthen extracted with acetone in a continuous extraction unit for 24 hoursand allowed to dry in air to give a blue powder.

To insure against lithium salt residues, the precipitation is repeated.Thus, there is produced 55.4 g. of a blue powder whose x-ray patternmatched that of the known published pattern for alpha metal-freephthalocyanine.

Preparation of Beta-Free Phthalocyanine A 10 g. supply of commercialMonolite Fast Blue GS is placed in a vycor dish which is then insertedin a 2- inch glass tube suitable for heating in a combustion tubefurnace. The temperature of the furnace is raised slowly to 350C. duringthe first 1% hours to avoid scattering of sample, and finally maintainedat 350 430C. during the next 4 hours. A stream of dry nitrogen is passedthrough the tube throughout the heat treatment. The treated sample istransferred to a desiccator for cooling, whereupon 9.45 g. of blue-blackpowder that gives an x-ray pattern consistent with that of the Betaformis obtained.

Preparation of X Form Metal-Free Phthalocyanine A 9 g. sample of alphametal-free phthalocyanine prepared by precipitation from sulfuric acidsolution,

and 90 g. of sodium chloride is placed in a quart-size porcelain ballmill and rolled at about 70 rpm for 72 hours.

The ground powder is removed manually from the mill and extracted with1500 ml. of 1 percent hydrochloric acid at 70 80C. for 1 hour. Theresultant slurry is filtered and the cake is washed repeatedly withdistilled water to remove the remaining sodium chloride. The cake isfinally rinsed with methanol several times and dried in air to give 8.8g. of blue powder. The x-ray diffraction pattern of this material cannotbe reconciled with any of the patterns published for the variouspolymorphic forms of metal-free phthalocyanine and agrees with thepatterns assigned to X-form as shown in FIGS. 1 and 11. Hence it isdesignated as the X form of metal-free phthalocyanine.

While the most effective plates are made by incorporation of the X formof metal-free pigment in resin binders, very good plates are also madewith the alpha metal-free form, particularly when this is converted toeither the beta by solvent recrystallization or X form in a coating aswill be described below. In order to identify the crystal form of thephthalocyanine pigment as it actually exists in the photoconductivelayer after the photoconductive layer is dried and cured, thephotoconductive coating is scraped off its substrate and powderedwithout any attempt to remove the surrounding resin (the latter does notseriously interfere with the measurement.) It is then filled into acapillary and various experiments are run on compressed powder pellets.The results of these experiments are recorded as above described in FIG. 1 (on alpha, beta, gamma and X form metal-free phthalocyaninepigments) in comparison with those of the literature.

Infrared measurements can be applied only to pigments without resinmatrix because, of course, the resin absorption interferes and masksthat of the pigment. The phthalocyanine pigment was suspended in a Nujolmull and subsequently examined in a standard infrared spectrophotometer(Perkin-Elmer Infracord Model No. 137). P16. ll shows the infraredspectra of these alpha, beta, gamma and X form metal-free pigments.

One type of transformation of crystal forms resulted in dramatic changesin crystal size and shape that could readily be observed under themicroscope while it was happening. This is the recrystallization ofunstabilized alpha metal-free phthalocyanine to beta metal-freephthalocyanine in a resin coating (VYNS and Epidene) which is treated bya suitable solvent vapor. The alpha pigment in the original coating isdeep blue, finely dispersed as amorphous appearing particles smallerthan about 10 microns. Upon treatment for from about 5 to minutes withhot vapors (at about from 170 180 of, for example. anthracene orphthalic anhydride. the color changes dramatically to a blue-green inthe treated areas. Simultaneously the crystallites grow intointerconnected stacks of fine needles which may be identified as nearlypure beta form of the pigment. The array of needles appears under themicroscope like a loosely matted pile of straw. The observed enhancementin photosensitivity may possibly be accounted for by the network ofneedles whose random arrangement present many points of near contactthroughout the thickness of the coating. The crystal change before andafter recrystallization is apparent by microscopic examination. t

While it is possible to make operable plates using commercial gradephthalocyanine pigments, such as Monolite Fast Blue GS (Arnold HoffmanCo., Division of ICI Limited), Heliogen Blue G (General Aniline FilmCorporation), or Cyan Green 15-3100 (American Cyanamid Corporation), thepurity control ordinarily exercised in the manufacture of these paint,ink and resin colorants is inadequate for large scale commerciallyreliable performance in xerographic devices. When commercial gradepigments are to be used, it is therefore desirable to purify them byknown procedures, such as solvent washing of the pigments, andsubsequent solution in concentrated sulfuric acid followed byprecipitation in ice-cold water. Various solvents can be used such asketones, alcohols, or chlorinated hydrocarbons. When such purificationprocedures were applied to typical commercial batches of, for example,Monolite Fast Blue GS, the photosensitivity of the resulting plates wasincreased by about 4 to 6 fold over unpurified controls and reached amore or less consistent value.

Still better results are obtained by special synthesis of pigments foruse in xerographic applications. The synthesis methods used are wellknown and are listed below with reference to the published literature,each process is discussed in Phthalocyanine Compounds" below cited.

A. Metal-Free Phthalocyanine 1. Alpha metal-free phthalocyanine wasprepared by each of the following synthesis routes:

a. methanolysis of dilithium phthalocyanine b. acid hydrolysis ofdilithium phthalocyanine, with optional reprecipitation from sulfuricacid.

2. Beta metal-free phthalocyanine was prepared from alpha formphthalocyanine by extended heating of the dry powder or by prolongedagitation in an aromatic solvent. Details of the preferred procedure arepres ented below.

3. Gamma metal-free phthalocyanine was prepared from calciumphthalocyanine by acid hydrolysis, ac-

cording to Phthalocyanine Compounds, by. Frank H.

Moser and Arthur C. Thomas, 1963 edition, published by ReinholdPublishing Corp.

4. X form metal-free phthalocyanine was prepared from alpha metal-freephthalocyanine by extended ball milling in salt particles followed bydesalting.

B. Metal Phthalocyanines The following metal phthalocyanine complexeswere used to make xerographic plates. These gave images which weregenerally inferior in contrast and photosensitivity to those obtainedwith metal-free phthalocyanine in comparable binders;

Chlorinated Copper phthalocyanine Beta Copper phthalocyanine Leadphthalocyanine Zinc phthalocyanine It was noticed that the performanceof these materials in part was a function of the binder used, forexample copper phthalocyanine and chlorinated copper phthalocyaninewhich were comparatively inferior in a vinyl resin (VYNS-3 vinylchloride-vinyl acetate copolymer) gave an acceptable image in a siliconebinder -(SR-82 dimethyl polysiloxane).

In the disclosure various tradenames will be used to define specificbinders and phthalocyanines. The following is a list of componentsidentified in the ensuing 11 1 disclosure identifying the basic chemicalstructure of each:

RESINS: Oxiron 2002 is an epoxidized polyolefin made by the FMCCorporation; VYNS-3 is a polyvinyl chloride-acetate copolymer made byUnion Carbide Corporation; Epidene 168/50 is a tall oil modified epoxyresin made by T. F. Washburn Company;

SR-82 is a silicone resin made by the General Electric Company;

Acryloid B-72 is a polyacrylate made by Rohm &

Haas Company;

Lucite 44 and 46 are polymethacrylates made by the DuPont Company;

PS-2 is a polystyrene resin made by the Pennsylvania Industrial ChemicalCompany;

Nitrocellulose made by the Hercules Powder Com- Pliolite S-7 is apolystyrene-butadiene copolymer RMD 451i is a styrene acrylonitrilecopolymer made by the Union Carbide Corporation;

Parlon is a chlorinated rubber made by the Hercules Powder Company;

Pliolite S-5, VT, VTL, VTLNX are all vinyl toluene polymers made by theGoodyear Chemical Company;

Vinac B-IOO is a vinyl acetate resin made by Air Reduction Company;

Tygon TP-lO7-B is an unpigmented metal primer made of a thermoplasticresin made and sold by US. Stoneware Company:

VMCH is a maleic acid modified acetate-vinyl chloride copolymer made bythe Union Carbide Corporation;

Synthetasine 200 is a thermosetting resin made by the lnterchemicalCorporation; DER 542 is a brominated epoxy resin made by the DowChemical Corporation.

The phthalocyanines used throughout this disclosure are identified asMonolite Fast Blue GS which is a mixture of alpha and beta metal-freephthalocyanine made by the Arnold Hoffman Company which is a Division of[C], Ltd.; Heliogen Blue G is a metal-free phthalocyanine; Heliogen BlueBGN is a copper phthalocyanine; Heliogen Green B, Heliogen Green andHeliogen Green RT are all chlorinated copper phthalocyanines made byGeneral Aniline and Film; Cyan Green 15-3100 is a chlorinated copperphthalocyanine made by American Cyanamid.

. It was pointed out above that certain crystal forms of the preferredpigment (metal-free phthalocyanine) are more light sensitive thanothers. Observations indicate that consistently the best plates areobtained if one starts with the stabilized X form of metal-freephthalocyanine and coats, dries and cures the plates under conditions inwhich this modification is preserved without substantialrecrystallization. The next best procedure is to start with alpha formpigment, and coat, dry and cure under conditions under which at leastsome of the alpha recrystallizes to either the X or beta form in thecoating. In fact, a novel solvent vapor treatment as will be describedbelow has been accomplished to achieve the transformation to the betaform deliber ately. In another preferred embodiment plates are preparedfrom the alpha form of the pigment without recrystallization during orafter coating. Comparatively poorer results were obtained in platesprepared solely from the beta modification of the pigment.

In summary, all crystal forms of metal-free phthalocyanines aredesirable for the present intended use, but the X form pigment is thepreferred material for simple,

economical manufacturing of xerographic plates of high sensitivity andexcellent reusability.

The recrystallization of alpha form phthalocyanines to the beta form incoating mixtures or in pre-existing coatings may be carried out by:

1. Inclusion of about 25 percent by volume of the high boilingrecrystallizing solvent in the coating mixture, and heating the plateduring the last stages of drying and curing. A number of solvents, whichhave been found to be suitable for this approach, particularly for usewith thermoplastic binder resins include benzyl benzoate, benzylether,dibenzylketone, N-methyl-N-phenylbenzamide, quinoline,alpha,2,4-trichlorotoluene, and suitable mixtures thereof.

2. Treatment of the dried coating with hot vapor of a recrystallizingagent. In the laboratory this may be achieved by placing the air driedresin plate face down over an evaporating dish containing therecrystallizing agent and subliming in an oven the latter compound ontothe plate for about 5 to 15 minutes. After the vapor treatment therecrystallizing agent and residual solvent are driven off by the bakinguntil no residues can be detected by appropriate analytical proceduressuch as vapor chromatography.

The following agents for examples are effective, particularly for use onthe thermoplastic vinyl resin plates: Acenaphthene, acridine,anthracene, benzophenone, phthalic anhydride, naphthalene, biphenyl, andmixtures thereof.

The specific phthalocyanine plates above defined have utility in eitherreusable and/0r single xerographic systems. The reusability of thephotoconductive layer of the present invention was established by aprocedure which can generally be described as follows.

The xerographic plate containing the phthalocyanine resinphotoconductive layer was charged, imaged and cascaded in commercialxerographic apparatus described as Xerox Number 1 Camera and using aXerox Flat Plate apparatus. The developer used was a commerciallyavailable xerographic developer such as is described in US. Pat. Nos.2,788,288; Re 25,136; and 3,079,342. The toner image waselectrostatically transferred to paper, the residual toner was releasedand wiped off in the normal fashion. The plates were then at least twicecylically re-charged, re-electrometered, re-exposed, and developed.

A wide variety of phthalocyanine plates in the preferred compositionrange were found to give reproducible electrometer reading and imageproperties. With organic resin binders plates beyond the high end of thepigment/resin ratio range were found to sively decreasing chargeacceptance.

Other plates were developed by means of liquid developers, by means ofaqueous pigment suspension, aerosol powders and frost deformation. Thephotoconductive layers were satisfactorily reusable in many cases. Itwas found that the reusability could be improved in some cases byinterposition of an extra charging step and blanket exposure between thefinal cleaning step of the proceeding imaging cycle and the initialcharging step of the next period. The reason for this observation is notcompletely understood. Reusability, particularly of highly pigmentedcoatings may be improved also by overcoating with a thin dielectriclayer.

give progres- The invention will be further described with reference tothe following examples, which describe in detail various preferredembodiments of the present invention. Parts, ratios and percentages areby weight unless otherwise stated.

All the materials tested below are charged, exposed and developed in theconventional Xerographic method and produce images ranging in quality.These images are designated in comparative terms in the ensuingexamples. Very good images are designated by the symbol A, good imagesare designated B, fair images C and weak images D.

EXAMPLES 1-7 An electrophotographic plate is prepared by initiallymixing six grams of Oxiron 2002 (an epoxidized poly- I olefin) and onegram X-form metal-free phthalocyanine (made by the process abovedescribed). This mixture is formulated together with 3.5grams phthalicanhydride, 9 grams n-butanol and 15 grams of acetone. The above mixtureis milled for about eight hours with porcelain pebbles in a 6-ouncemixing vessel. To form the plates the resulting mixture is deposited ona bright finish ml. aluminum foil with a No. 40 drawdown rod. Thecoating is cured for about 60 minutes at about 175C.

Seven platescontaining the photoconductive layer above defined areprepared for subsequent testings as indicated in the following table. Itshould be noted that each of the plates prepared contain thephotoconductive layer without an overcoating. The seven plates aretested for positive charge acceptance (one pass under the corotron at8.7 KV) and charge retention after ex- 14 Charge Charge Retention PlateAcceptance Volts After Image Number Volts Exposure Quality 1 580 A 2 63010 A 3 630 10 A 4 620 10 A 5 610 10 A 6 670 10 A 7 630 10 A Mixturesusing the specific phthalocyanine-resin binder are prepared by ballmilling the phthalocyanine pigment in a solution of a resinous binderand one or more solvents until the pigment is well dispersed. Thedesired parts of phthalocyanine are added to the desired parts of resinsolution in a suitable mixing vessel. Porcelain pebbles are added untilthe liquid just covers the pebbles. Milling is on rolls which are run atsuch speeds that the jar moves at about rpm. Approximately 8 hoursmilling is required to achieve good dispersions of those phthalocyanineswhich are dispersed by this procedure and use any phthalocyanine toresin ratios of about 1 to 100. The milled mixture may be stored priorto decomposition on the supporting substrate.

Aluminum foils are used as the supporting substrate and the finsihedcoatings are obtained by applying the coating mixture to the foil,flowing it back and forth and then allowing it to drain by gravity fromthe plate suspended so thatthe plane is essentially vertical or arecoated with a drawdown rod. The coated plate is allowed to air dry andthen is ready for precharge processing which may be merely heat curingthe resin or may involve a recrystallization step. The recrystallizingagent may be sublimed up onto the coated plate to reerystallize in situor be added to the coating mixture before coating on the aluminum foil.

EXAMPLES 8-10 The phthalocyanine used in these examples is Monolite FastBlue GS in varying degrees of purity; the plate is made by the methoddescribed above. The following results are obtained using this Monolitewith VYNS-3 as the film fonning resin.

(acetone extracted and acid precipitated) pos u're to 3-foot candleseconds of photoflood illumin a 'tion. Results are as follows:

The acetone treatment of the Monolite removes organic solublenon-phthalocyanine residual impurities.

i i I 1 The acid (sulfuric) treatment removes at least some of EXAMPLES7-28 the inorganic impurities and Converts the Phthalocya- Thephthalocyanines used in these examples are all nine to the alpha formmetal phthalocyanines which may be made by methods described in J. Chem.Soc. (1936) l7l9-l736. The

EXAMPLES 11-16 5 .plates are made by the method indicated above, and Theresin to phthalocyanine weight ratio used is of upon testing give thefollowing results:

M Resin: Charge Phthalo- Retention Film Cyanine Charge After Phthalo-Forming Weight Acceptance Exposure Image Cyanine Resin Ratio Volts VoltsQuality Heliogcn Blue-BGN VYNS-3 9:] 9O 50 C Heliogcn not not Green-BSR-82 48:] available available C Heliogen Green-B VYNS-3 9:1 70 50 DHeliogcn Green-RT SR-XZ 485] 860 500 B Heliogen Green-Toner 66-300lSR-82 48:] I000 900 C Heliogen A Green-Toner 66-3001 VYNS-3 9:1 100 70Aluminum VYNS-3 6:1 50 40 Lead VYNS-3 6:1 80 75 Copper HexadecabromoVYNS-3 6:] l 80 D Copper Hexadecaehloro SR-82 60:] l 100 900 D CopperVYNS-3 6:1 300 240 Cyan Green Toner l5-3l00 SR-82 48:] 500 275 Csignificant importance in obtaining desirabie results. EXAMPLES 29-44The variation in results is illustrated by the below runs M t l fphthalocyanines in a variety f resin i where the same components ar sedin ryi g ers are used to produce a xerographic image. Excepamounts.Epidene res/50am Monolite Fast Blue GS tionally good imagequality isobtained with these metare used to make the photoconductive layer i llthe al-free phthaloeyanmes. The results are indicated beplates tested;tl' lgt'fiSlllLSilLB QifQHQW Z WWW 10W Resin: Phthalocyanine ChargeCharge Weight Acceptance Retention image Ratio Volts Volts Quality l00:l660 560 D 630 I70 C 25:! 530 B l9:l 650 30 A |0;l 460 23 A 41l 300 5 AResin to Charge Phthalo- Charge Retention Cyanine Acccpt- Volts-Phthalo- Weight ance After image Cyanines Resin Ratio Volts ExposureQuality X-form epoxyphenolic (1; I 450 20 A Alpha to X-formepoxyphenolic 6:1 480 25 A Alpha to beta form epoxyphenolic 63l 520 IS AX-torm cpoxidized polyolefin 6:! 630 10 A Rcsin to Charge Phthalo-Charge Retention Cyanine Accept- Volts- Phthalo- Weight -ance AfterImage Cyanines Resin Ratio Volts Exposure Quality *Alpha m X-formcpoxidized polyolefin 6:1 360 5 X-form phenolic 6:] 550 10 A Alpha formphenolic 6:1 3 l A X-form epoxy-ureaformaldehyde 6:] 640 A X'fnrmepoxy-B.P.A.

resin 6:] 630 5 A Alpha form B.P.A.-epoxyurea formaldehyde copolymcr4.5:l 490 60 A X-l'orm lull-oil modified epoxy 3:1 350 t (l A X-formtall-oil modified epoxy (vl 400 5 A X-lorm tall-oil modified epoxy l0:l550 5 A X-form copolymer of B.P.A. and epichlorohydrin |4:I 290 A X-formpolyvinyl chloride acetate copolymer 6: l 90 I5 -X-form RMD-l 1 10:1 450B.P.A. bisphenol A Alpha converted to the X-fonn in situ Alpha convertedto the beta form in situ As noted earlier in this disclosure, the choiceof binder is an important consideration in preparation of thexerographic plate. While positive results are obtained (image produced)with all of the following resins, the image quality varied within arelatively large area. The photoconductive layer is made by milling the40 phthalocyanine with the resin solution until the desired dispersionis obtained, then applying the mix to a supporting substrate. Thephthalocyanine used in all the following runs is Monolite Fast Blue GS.The following table indicates the results:

EXAMPLES 57-105 tive layer for use on a reusable xerographic plate.

These resins are investigated in reusability tests as described above;the results are as follows:

BEE'SL V V V a V, PHTH QCY M RESIN PIBIHALOCYANLNEAWEIGHI RATIOREUSABlLlTY RAT1NG* Araldite 571-K Monolite Fast 17.5/1

Blue GS 35/1 Araldite 6040 Monolite Fast Phthalic Anhydride Blue GS 50/1C Araldite 6040 Monolite Fast Furoic acid Blue GS 33/1 C Araldite 6040Monolite Fast RMD 4511 Blue GS 16/1 B Araldite 6040 Monolite Fast RMD4511 Blue GS 23/1 C AraIdite-57l-K-7O Monolite Fast Araldite 6040 BlueGS 43/1 B Araldite 6040 Monolite Fast VYHH 7 Blue GS 22/1 B Araldite6040 Monolite Fast VYHH Blue GS 27/13 B Araldite 6040 Monolite FastEponol 55-B-40 Blue GS 33/1 C Aralditc 6040 Monolite Fast Eponol 55-B-40Blue GS 20.5/1 C Araldite 6040 Monolite Fast Eponol 55-B-40 Blue GS2072/1 C DC Silicone Monolite Fast R-5061 Blue GS 20/1 B DC SiliconeMonolite Fast R-5061 Blue GS 10/1 B Epidene 168/50 Monolite Fast Blue GS25/1 B Epidene 168/50 Monolite Fast Blue GS 12.5/1 B Epidenc 168/50X-form 25/1 8 Epidene 168/50 plus cobalt or Monolite Fast manganesedriers Blue GS 25/1 C Geon 222 Monolite Fast Blue GS 10/1 C ParlonMonolite Fast Blue GS 31/1 C Pliolite S-5 Monolite Fast Blue GS 10]] BPliolite VT Monolite Fast Blue GS 10/1-14/1 B Pliolite VTL Monolite FastBlue GS 10/1 B Pliolite VTLMX Monolite Fast Blue GS 10/1 B RMD 4511Monolite Fast Blue GS 6/1 B RMD 451 l Monolite Fast Blue GS 8/1 B RMD451 1 Monolite Fast Blue GS 10/1 B RMD 451 1 X-form 9/1 B RMD 4511X-form 10/1 B RMD 4511 X-form 10/1 B RMD 451 l X-form 10/1 B RMD 4511X-form 20/1 B RMD 4511 X-form 30/1 B Vinac B-l00 Monolite Fast Blue GS7.5/1 B RESIN: A PHTHALOCYANINE REUSABlLlTY RESIN PHTHALOYANTNE WEIGHTRATIO RATING Vinyl-epoxy Monolitc Fast copolymer Blue GS 18/1-25/l I C ITygon TP-IO7B Monolite Fast Blue GS 10/1 C VMCH Monolite Fast 7 n n A 7v Bldos' A w 10/1 C Oxiron 2002 X-form 6/ l Epoxy-phenolic Monolite FastBlue GS 6/1 A Epoxy-phenolic Alpha to X form in situ 6/1 AEpoxy-phenolic Alpha to beta in situ 6/1 A Epoxy-phenolic 4 X-form 6/1 AEpoxy-phenolic X-form l A Epoxy-phenolic Beta form 6/1 A Phenolic X-form5/1 A Epoxy-urea formaldehyde resin X-form A Epoxy-phenolic Alpha toX-form 2/1 Epoxy-phenolic X form' 12/] w A K iiodiusiihilii l W B fairrcusability C poor rcusability EXAMPLES 166-1 16 35 in 50 ml. ofethanol. To this solution is added 0.5 ml.

of AB sensitizer (a dichromate solution) which is sold Some of thephotoconductive layers are adapted by the Colonial Processing SupplyCompany. After the more readily for reusability than others, while manyof solution is mixed about two drops of a 30 percent aquethe lessreusable plates are improved significantly by ous ammonia solution isadded. This solution is applied overcoating. The overcoating is madefrom a mixture 40 to the plate by drawdown using a Number 14 rod.

containing'S m1. of a solution of 5 grams orange shellac The results ofvarious resins are indicated below:

RE USABILITY RESIN TO WITH 0R RESIN PHTHALOCYANINE WITHOUTPHIHALOCYANINE WEIGHT RATIO OVERCOATING Epidene 168/50 X-form 3:1 B

Epidene 168/50 xiomi 25:1 1 B Araldite 571K X-form 6:] A

Epoxy-phenolic Alpha to beta in situ 6:] A

Epoxy-phenolic X-form 6:] A

Epoxy-phenolic X-form 4:1 A Epoxy-phenolic Beta form 6. l A

Phenolic x-roim 6:1 A

Epoxy-ureaformaldehyde X-forrrl 6:1 A Epoxy-phenolic Alpha to X-form insitu l2:1

Epoxy-phcnolic X-f0rm l 2:1 A

A-rcusahle Without overcoating B-rquircs overcoating for rcusahilityEXAMPLES 117-127 A variety of plates are made which are reusable and acomparison is made of the image quality of the first and last imagesformed. The quality varies, as does the number of images made withvarious plates.

Results of tests on reusability of both overcoated and unovercoatedplates are indicated in the following table:

RESIN T NUMBER EXAMPLES 130 131 PHTHALOCYANINE PHTHALO- OF EVALUATIONEVALUATION AND CYANlNE IMAGES OF FIRST OF LAST RESIN RATlO MADE IMAGE VIMAGE Epidene l68/50 X-form 3:1

Epidene 168/50 *25zl 7 A and X-form X-form and Aralditc 571K 6:l 5 A AAlpha to beta in situ Epoxy-phenolic 6:1 5 A A X-form and Epoxy-phenolic6:! 5 A A X-form mid Epoxy-phenolic 4:] 5 A A Beta form andEpnxy-phcnnlic 6:! 5 A X-form and Phenolic 6:] 5 A X-fnrm and epoxy-ureaformaldehyde 6:! 5 A A Alpha to X-form in situ and Epoxy-phenolic l2:l 5A A X-form and Epoxy Phenolic 12:1 5 A r A overcoated plates A very goodimages EXAMPLE 128 One part of alpha-form metal free phthalocyaninepowder is blended with five parts by weight of powdered selenium on analuminum plate and spread in a uniform layer over the plate surface.This mixture is then heated above 217C. (the melting point of selenium)so that the molten selenium wets the phthalocyanine particles and thewhole plate is then quenched in water to prevent crystal growth andretain the selenium in its amorphous form. The plate is then charged,exposed and developed by conventional xerographic techniques and itsresponse is compared with that of an ordinary amorphous seleniumxerographic plate containing no phthalocyanine. A very noticeableincrease in red light response and overall photographic sensitivity isobserved.

EXAMPLE 129 the othefportiori o f the hot melt there is added one partby weight of the alpha form of metal-free phthalocyanine to each 5 partsby weight of the hot melt which is then coated on a similar aluminum.Each of these plates is then allowed to cool and tested according to theprocedure of Example 128. While images are produced on both plates, amuch increased response in the red end of the visible spectrum andfaster overall speed is evidenced by the Example 131 plate.

EXAMPLES 132 133 Fifty parts by weight of 2,5-bis(p-aminophenyl),1,3,4-oxadiazole, 50 parts by weight of an /15 copolymer of vinylchloride and vinyl acetate and 5 parts by weight of2,4,7-trinitrofluorenone are dissolved in sufficient toluene to make afree-flowing solution which is divided in two halves. The first half iscoated on a sheet of aluminum foil and force dried in a warming oven. Tothe other half of the solution there is added one part of the alpha formof metal-free phthalocyanine to each 6 parts of dissolved solidsfollowed by vigorous agitation to disperse the phthalocyanine particlesthroughout the solution. The suspension thus formed is then coated on asecond sheet of aluminum foil and force dried under the same conditionsemployed to dry the plate of Example 130. Both plates are then testedaccording to the procedure of Example 128 and although they aresignificantly slower than the plates of Examples 130 and 131, therestill seems to be very significantly higher red response and higheroverall light sensitivity in the film containing the metal-free.phthalocyanine as compared with the one which does not.

EXAMPLE 134 Six parts by weight of the X-form of metal-freephthalocyanine is well dispersed in 5 parts by weight of a very lowmelting glass enamel frit. This particle mixture is then applied to auniform thickness over the surface of a stainless steel plate which isthen fired under I a vacuum to melt the glass and rapidly cool to roomtemperature. After breaking the vacuum, the plate is tested according tothe procedure of Example 128 and found to produce a good qualityxerographic image with significant response in the red portion of thevisi- 2O ble spectrum.

EXAM PEE'TQ One part by weight of X-phthalocyanine is dispersed to 6parts by weight of melted sucrose. The mixture is coated onto analuminum plate to a uniform thickness and cooled to room temperature.The plate is xerographically charged and exposed. It retains charge,

shows good photoresponse, and can be imaged and de- 3 veloped bystandard xerographic techniques. Sensitivity is excellent.

EXAMPLE 136 A melt of boric acid (Baker Analyzed Reagent) is prepared byheating the boric acid in an oven at 240C. One part by weight ofX-phthalocyanine is well dispersed in 6 parts of the boric acid melt.The mixture is coated onto an aluminum plate and cooled to roomtemperature. The resultant xerographic layer can be charged and imagedbut its sensitivity is only about l/lO that of the sucrose plate ofExample 135.

Although various embodiments are directed specifically to the aboveexamples, many of the typical matethese are intended to be encompassedwithin the scope 5 of this invention.

What is claimed is:

1. 'An electrophotographic material comprising phthalocyanine pigmentparticles dispersed in a binder material and a spectral sensitizingagent for said phthalocyanine pigment, said phthalocyanine particlesbeing present in said binder in an amount up to about 50 percent byweight and said binder having a resistivity greater than about 10ohm/cm.

. 6 2. An electrophotographic plate which comprises a 5 photoconductivelayer substantially uniformly coated to a thickness of up to about 80microns on a substrate material, said photoconductive layercomprisingphthalocyanine pigment particles dispersed in a bindermaterial, said phthalocyanine being selected from the group consistingof beta-form phthalocyanine and X-form phthalocyanine and mixturesthereof, and said binder material having a resistivity greater thanabout 10 ohm/cm.

3. The plate of claim 2 wherein said phthalocyanine pigment particlesare present in said binder material in an amount up to about 50 percentweight.

4. The plate of claim 2 wherein said phthalocyanine pigment particlesare metal-free.

5. The plate of claim 2 wherein said substrate material comprises paper.

6. The plate of claim 2 wherein said substrate material is substantiallyconductive.

7. The plate of claim 2 further comprising a substantially dielectricovercoating material overlying said photoconductive layer.

8. The plate of claim 2 wherein'said binder material is substantiallyphotoconductive.

9. The plate of cla1m 8 wherein said binder comprisespolyvinylcarbazole.

l0. The plate of claim 8 wherein said binder comprises selenium.

11. An electrophotographic process wherein the plate of claim 2 iselectrostatically charged and exposed to a pattern of activatingelectromagnetic radiatlon.

12. An electrophotographic process wherein the plate of claim 2 iselectrically charged, exposed to an image pattern to be reproduced anddeveloped with electroscopic marking particles.

13. An electrophotographic process which comprises passing the plate ofclaim 2 at least twice through a cycle comprising charging and exposingsaid plate to a pattern of activating electromagnetic radiation anddeveloping.

14. A process for forming an image which comprises exposing in imagewiseconfiguration a photoconductive layer positioned on a paper substratematerial, said layer comprising phthalocyanine pigment dispersed in abinder material to form a latent electrostatic image, and developingsaid image.

15. A process for forming an image which comprises exposing in imagewiseconfiguration a photoconductive layer comprising phthalocyanine pigmentdispersed in a binder material to form a latent electrostatic image, anddeveloping said image.

16. The process of claim 15 wherein said photoconductive layer isovercoated with an insulating composition.

17. The process of claim 15 wherein at least one image is formed at thesurface of said photoconductive layer.

18. A process for forming a latent electrostatic charge pattern whichcomprises electrostatically charging a photoconductive layer comprisingphthalocyanine pigment dispersed in a binder material,and exposing saidlayer to a pattern of activating electromagnetic radiation.

19. A process for forming a latent electrostatic charge pattern on anelectrophotographic plate, said plate comprising a photoconductive layercomprising phthalocyanine pigment dispersed in a binder material, inelectrical contact with a supporting substrate, which compriseselectrostatically charging the photoconductive layer of said plate andexposing said layer to a pattern of activating electromagneticradiation.

20. An electrophotographic process which comprises electrically chargingan electrophotographic plate, said plate comprising phthalocyaninepigment dispersed in a binder material, exposing said plate to an imagepattern to be reproduced, and developing said image.

21. An electrophotographic process which comprises passing anelectrophotographic plate at least twice through a cycle comprisingcharging and exposing said plate to a pattern of activatingelectromagnetic radiat ioii and developing with electrically attractable marking material.

22. A process for forming a latent image which comprises exposing inimagewise configuration a photoconductive composition comprising amatrix of a substantially non-photoconductive organic polymer containinga substantially uniform dispersion of particles of a photoconductivepigment selected from the group consisting of phthalocyanine and metalderivatives of phthalocyanine.

23. A process for forming a latent electrostatic charge pattern whichcomprises electrostatically charging and exposing a photoconductivecomposition comprising a matrix of a substantially non-photoconductiveorganic polymer containing a substantially uniform dispersion ofparticles of a photoconductive pigment selected from the groupconsisting of phthalocyanine and metal derivatives of phthalocyanine.

24. A process for forming a latent electrostatic charge pattern on anelectrophotographic plate, said plate comprising a supporting substratein electrical contact with a photoconductive composition comprising amatrix of a substantially non-photoconductive organic polymer containinga substantially uniform dispersion of particles of photoconductivepigment selected from the group consisting of phthalocyanine and metalderivatives of phthalocyanine, which comprises electrostaticallycharging and exposing said photoconductive composition.

25. An electrophotographic process which comprises electrically chargingan electrophotographic plate, said plate comprising a photoconductivecomposition comprising a matrix of a substantially non-photoconductiveorganic polymer containing a substantially uniform dispersion ofparticles of a photoconductive pigment selected from the groupconsisting of phthalocyanine and metal derivatives of phthalocyanine,exposing said plate to an image pattern to be reproduced, and developingwith electrostatically attractable marking material.

26. A process for forming a latent image which comprises exposing inimagewise configuration a photoconductive layer comprisingphthalocyanine pigment particles dispersed in a binder material, saidphthalocyanine being a primary photosensitive material in said layer andbeing present in said photoconductive layer in an amount up to about 50percent by weight.

27. A process for forming a latent electrostatic charge pattern whichcomprises electrostatically charging a photoconductive layer andexposing said layer to a pattern of activating electromagneticradiation, said photoconductive layer comprising phthalocyanine pigmentparticles dispersed in a binder, said phthalocyanine being a primaryphotosensitive material in said layer and being present in saidphotoconductive layer in an amount up to about 50 percent by weight.

2. An electrophotographic plate which comprises a photoconductive layersubstantially uniformly coated to a thickness of up to about 80 micronson a substrate material, said photoconductive layer comprisingphthalocyanine pigment particles dispersed in a binder material, saidphthalocyanine being selected from the group consisting of beta-formphthalocyanine and X-form phthalocyanine and mixtures thereof, and saidbinder material having a resistivity greater than about 1010 ohm/cm. 3.The plate of claim 2 wherein said phthalocyanine pigment particles arepresent in said binder material in an amount up to about 50 percentweight.
 4. The plate of claim 2 wherein said phthalocyanine pigmentparticles are metal-free.
 5. The plate of claim 2 wherein said substratematerial comprises paper.
 6. The plate of claim 2 wherein said substratematerial is substantially conductive.
 7. The plate of claim 2 furthercomprising a substantially dielectric overcoating material overlyingsaid photoconductive layer.
 8. The plate of claim 2 wherein said bindermaterial is substantially photoconductive.
 9. The plate of claim 8wherein said binder comprises polyvinylcarbazole.
 10. The plate of claim8 wherein said binder comprises selenium.
 11. An electrophotographicprocess wherein the plate of claim 2 is electrostatically charged andexposed to a pattern of activating electromagnetic radiation.
 12. Anelectrophotographic process wherein the plate of claim 2 is electricallycharged, exposed to an image pattern to be reproduced and developed withelectroscopic marking particles.
 13. An electrophotographic processwhich comprises passing the plate of claim 2 at least twice through acycle comprising charging and exposing said plate to a pattern ofactivating electromagnetic radiation and developing.
 14. A process forforming an image which comprises exposing in imagewise configuration aphotoconductive layer positioned on a paper substrate material, saidlayer comprising phthalocyanine pigment dispersed in a binder materialto form a latent electrostatic image, and developing said image.
 15. Aprocess for forming an image which comprises exposing in imagewiseconfiguration a photoconductive layer comprising phthalocyanine pigmentdispersed in a binder material to form a latent electrostatic image, anddeveloping said image.
 16. The process of claim 15 wherein saidphotoconductive layer is overcoated with an insulating composition. 17.The process of claim 15 wherein at least one image is formed at thesurface of said photoconductive layer.
 18. A process for forming alatent electrostatic charge pattern which comprises electrostaticallycharging a photoconductive layer comprising phthalocyanine pigmentdispersed in a binder material, and exposing said layer to a pattern ofactivating electromagnetic radiation.
 19. A process for forming a latentelectrostatic charge pattern on an electrophotographic plate, said platecomprising a photoconductive layer comprising phthalocyanine pigmentdispersed in a binder material, in electrical contact with a supportingsubstrate, which comprises electrostatically charging thephotoconductive layer of said plate and exposing said layer to a patternof activating electromagnetic radiation.
 20. An electrophotographicprocess which comprises electrically charging an electrophotographicplate, said plate comprising phthalocyanine pigment dispersed in abinder material, exposing said plate to an image pattern to bereproduced, and developing said image.
 21. An electrophotographicprocess which comprises passing an electrophotographic plate at leasttwice through a cycle comprising charging and exposing said plate to apattern of activating electromagnetic radiation and developing withelectrically attractable marking material.
 22. A process for forming alatent image which comprises exposing in imagewise configuration aphotoconductive composition comprising a matrix of a substantiallynon-photoconductive organic polymer containing a substantially uniformdispersion of particles of a photoconductive pigment selected from thegroup consisting of phthalocyanine and metal derivatives ofphthalocyanine.
 23. A process for forming a latent electrostatic chargepattern which comprises electrostatically charging and exposing aphotoconductive composition comprising a matrix of a substantiallynon-photoconductive organic polymer containing a substantially uniformdispersion of particles of a photoconductive pigment selected from thegroup consisting of phthalocyanine and metal derivatives ofphthalocyanine.
 24. A process for forming a latent electrostatic chargepattern on an electrophotographic plate, said plate comprising asupporting substrate in electrical contact with a photoconductivecomposition comprising a matrix of a substantially non-photoconductiveorganic polymer containing a substantially uniform dispersion ofparticles of photoconductive pigment selected from the group consistingof phthalocyanine and metal derivatives of phthalocyanine, whichcomprises electrostatically charging and exposing said photoconductivecomposition.
 25. An electrophotographic process which Compriseselectrically charging an electrophotographic plate, said platecomprising a photoconductive composition comprising a matrix of asubstantially non-photoconductive organic polymer containing asubstantially uniform dispersion of particles of a photoconductivepigment selected from the group consisting of phthalocyanine and metalderivatives of phthalocyanine, exposing said plate to an image patternto be reproduced, and developing with electrostatically attractablemarking material.
 26. A process for forming a latent image whichcomprises exposing in imagewise configuration a photoconductive layercomprising phthalocyanine pigment particles dispersed in a bindermaterial, said phthalocyanine being a primary photosensitive material insaid layer and being present in said photoconductive layer in an amountup to about 50 percent by weight.
 27. A process for forming a latentelectrostatic charge pattern which comprises electrostatically charginga photoconductive layer and exposing said layer to a pattern ofactivating electromagnetic radiation, said photoconductive layercomprising phthalocyanine pigment particles dispersed in a binder, saidphthalocyanine being a primary photosensitive material in said layer andbeing present in said photoconductive layer in an amount up to about 50percent by weight.